Water treatment control systems and methods of use

ABSTRACT

The control systems and technique can regulate or control operations of a water treatment system in a primary control mode and, when appropriate, in a secondary or an alternate control mode. The primary control can represent a normal control mode during which the water treatment system is intended to operate. The alternate control mode can represent a second control or mode of operation. The systems can be operated to control or facilitate regulation, monitoring, and performance of one or more operating parameters of one or more water systems between, or to and from, a first mode, a second or alternate mode, and, in some cases, a third or even a fourth control mode. The change in control mode can be triggered by identifying one or more predetermined, pre-selected, and/or programmed conditions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to water and wastewater treatment systems orfacilities, and components thereof, as well as to methods, and actsthereof, of treating water and/or wastewater and, in particular, tocontrolling and control systems of water and/or wastewater treatmentsystems or facilities.

2. Description of Related Art

Treatments of water and components and/or systems thereof are disclosed.For example, Pomeroy, in U.S. Pat. No. 2,289,589, discloses thetreatment of aqueous liquids with halogens. Oldershaw et al., in U.S.Pat. No. 3,351,542, disclose electrolytic chlorination and pH control ofswimming pool water. Crane et al., in U.S. Pat. No. 3,458,414, disclosea swimming pool water conditioner. Kirkham et al., in U.S. Pat. No.3,669,857, disclose electrolytic chlorination and pH control of water.Bishop et al., in U.S. Pat. No. 3,733,266, disclose waste waterpurification by breakpoint chlorination and carbon adsorption. Bachhoferet al., in U.S. Pat. No. 4,053,403, disclose a method of treating anddegerminating water. Eichenhofer et al., in U.S. Pat. No. 4,056,469,disclose the purification of waste water from hydrazine production.Tighe et al., in U.S. Pat. No. 4,129,493, disclose a swimming poolchlorinator system. Persson et al., in U.S. Pat. No. 4,136,005, disclosean electrolytic chlorinator. Heimberger et al., in U.S. Pat. No.4,137,166, disclose a process for the purification of waste watercontaining ammonia and ammonia salts. Sato et al., in U.S. Pat. No.4,149,952, disclose an electrolytic cell. Sweeney, in U.S. Pat. No.4,256,552, discloses a chlorine generator. Mose et al., in U.S. Pat. No.4,263,119, disclose anode elements for monopolar filter presselectrolysis cells. Adams et al., in U.S. Pat. No. 4,340,489, disclose awastewater treatment process with pH adjustment. Mihelic et al., in U.S.Pat. No. 4,366,064, disclose treatment of blast furnace wastewater. Reiset al., in U.S. Pat. No. 4,385,973, disclose a process for disinfectingwater. Delaney et al., in U.S. Pat. No. 4,393,037, disclose a method forreconditioning bacteria-contaminated hydrogen sulfide removing systems.Iijima et al., in U.S. Pat. No. 4,409,074, disclose a process forelectrolysis of an aqueous alkali metal chloride solution. Bachot etal., in U.S. Pat. No. 4,432,860, disclose a porous diaphragm forelectrolytic cells. Bianchi, in U.S. Pat. No. 4,496,452, discloses anapparatus and process for producing chlorine gas and for employing suchchlorine gas for the production of chlorine water. Burrus, in U.S. Pat.No. 4,508,697, discloses hypochlorite destruction using urea. McCollum,in U.S. Pat. No. 4,550,011, discloses a sample flow cell for automatichalogen and pH control for water reservoirs. Samejima et al., in U.S.Pat. No. 4,574,037, disclose a vertical type electrolytic cell andelectrolytic process using the same. Hilbig, in U.S. Pat. No. 4,599,159,discloses an electrolytic pool chlorinator having a distribution chamberfor filling anode and cathode chambers. Tetzlaff et al., in U.S. Pat.No. 4,627,897, disclose a process for the electrolysis of liquidelectrolytes using film flow techniques. Conlan, in U.S. Pat. No.4,818,412, discloses an apparatus and process for feeding hypochloritesolution. Brouzes et al., in Canadian Patent No. 1079423, disclose aprocess for treating waste water. Kiyohiko, in Japanese PatentApplication Publication No. 60202792, discloses an apparatus foroxidation and reduction treatment. Nakao et al., in U.K. PatentApplication Publication No. GB2027004, disclose a method of treatingnitrite-containing waste water.

Water treatment control systems are also disclosed. For example, Wall,in U.S. Pat. No. 4,033,871, discloses an integrated monitor and controlsystem for continuously monitoring and controlling pH and free halogenin swimming pool water. Steininger, in U.S. Pat. No. 4,224,154,discloses a swimming pool chemical control system. Zabel, in U.S. Pat.No. 4,323,092, discloses an apparatus and process for detecting freechlorine. Russell et al., in U.S. Pat. No. 4,381,240, disclose aswimming pool water conditioning system. Matsko, in U.S. Pat. No.4,435,291, discloses a breakpoint chlorination control system. Aragon,in U.S. Pat. No. 4,767,511, discloses a chlorination and pH controlsystem. Kim et al., in U.S. Pat. No. 5,348,664, disclose a process fordisinfecting water by controlling oxidation/reduction potential.

SUMMARY OF THE INVENTION

In accordance with one or more embodiments, the invention can provide amethod of controlling addition of an oxidizing compound to a watertreatment system. The method can comprise measuring a value of a processparameter of the water treatment system, generating a first controlsignal in a first control mode when the value of the process parameteris within a first range, and generating a second control signal in asecond control mode when the value of the process parameter is within asecond range.

In accordance with one or more embodiments, the invention can provide amethod of controlling addition of an oxidizing compound to a watertreatment system. The method can comprise specifying a first set pointrepresenting a first desired operating condition of the water treatmentsystem, specifying a second set point and a tolerance representing asecond desired operating condition of the water treatment system,generating a first input signal corresponding to a first operatingparameter of the water treatment system, generating a second inputsignal corresponding to a second operating parameter of the watertreatment system, generating a first output signal based on a differencebetween the first input signal and the first set point when a differencebetween the second input signal and the second set point is less thanthe tolerance, and generating a second output signal based on the firstinput signal and a second set point when the difference between thesecond input signal and the second set point is greater than thetolerance.

In accordance with one or more embodiments, the invention can provide amethod of controlling addition of a compound to a water treatmentsystem. The method can comprise specifying a primary set pointrepresenting an operating condition of the water treatment system;measuring a primary operating parameter and a secondary operatingparameter of the water treatment system; generating a first outputsignal based on the primary operating parameter and the primary setpoint; identifying an alternate control mode when at least one conditionselected from the group consisting of a low first operating parameter, ahigh first operating parameter, a low second operating parameter, and ahigh second operating parameter is present; and generating an alternateoutput signal based on at least one of the primary operating parameterand the secondary operating parameter when the alternate control mode isidentified.

In accordance with one or more embodiments, the invention can provide awater treatment system. The water treatment system can comprise an inputdevice disposed to measure an operating parameter of the water treatmentsystem and generate a corresponding input signal; a controller disposedto receive and analyze the input signal and generate a first outputsignal, in a first control mode, based on a first difference between theinput signal and a first set point value and a second output signal, ina second control mode, based on a second difference between the inputsignal and a second set point value; and an output device disposed toreceive the first and second output signals and regulate addition of anagent to the water treatment system.

In accordance with one or more embodiments, the invention can provide awater treatment system comprising a first measurement device disposed tomeasure a first parameter of the water treatment system and generate afirst input signal, a second measurement device disposed to measure asecond parameter of the water treatment system and generate a secondinput signal, a controller disposed to receive and analyze the firstinput signal and the second input signal and generate a first outputsignal when a difference between the second input signal and a secondset point value is less than a tolerance and generate a second outputsignal when the difference between the second input signal and the setpoint value is greater than the tolerance, and an output device disposedto receive at least one of the first and second output signals andregulate addition of an oxidizer to the water treatment system.

In accordance with one or more embodiments, the invention can provide awater treatment system comprising an ORP sensor disposed in the watertreatment system; an amperometric sensor disposed in the water treatmentsystem; a means for controlling addition of an oxidizing species towater in the water treatment system in response to a signal from atleast one of the ORP sensor and the amperometric sensor; and a means foridentifying and controlling addition of the oxidizing species in analternate control mode in response to a signal from at least one of theORP sensor and the amperometric sensor when at least one conditionselected from the group consisting of a low first operating parameter, ahigh first operating parameter, a low second operating parameter, and ahigh second operating parameter is present.

In accordance with one or more embodiments, the invention can provide acomputer-readable medium having computer-readable signals stored thereonthat define instructions that, as a result of being executed by acomputer, instruct the computer to perform a method of controllingaddition of an oxidizer compound to a water treatment system comprisingacts of generating a first control signal in a first control mode when avalue of a process parameter of the water treatment system is within afirst range and generating a second control signal in a second controlmode when the value of the process parameter is within a second range.

In accordance with one or more embodiments, the invention can provide acomputer-readable medium having computer-readable signals stored thereonthat define instructions that, as a result of being executed by acomputer, instruct the computer to perform a method of controllingaddition of an oxidizer compound to a water treatment system comprisingacts of receiving a first input signal from a first input devicedisposed to measure a first operating parameter of the water treatmentsystem, receiving a second input signal from a second input devicedisposed to measure a second operating parameter of the water treatmentsystem, generating a first output signal based on the first input signaland a first set point when a difference between the second input signaland the second set point value is less than a tolerance, and generatinga second output signal based on the first input signal and a second setpoint when the difference between the second input signal and the secondset point value is greater than the tolerance.

Other advantages, novel features, and objects of the invention shouldbecome apparent from the following detailed description of the inventionwhen considered in conjunction with any accompanying drawings, which areschematic and not intended to be drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred, non-limiting embodiments of the invention will be describedby way of example with reference to the following, accompanyingdrawings. In the drawings, each identical or nearly identical componentthat is illustrated in any of the various drawings may be typicallyrepresented by a like numeral. For clarity, not every component may belabeled in every drawing and not every component may be shown whereillustration is not necessary to allow a person of ordinary skill in theart to understand the invention. In the drawings:

FIG. 1 is a schematic diagram of a water treatment system in accordancewith one or more embodiments of the invention;

FIG. 2 is a flow diagram representatively illustrating at least aportion of the steps or acts utilized in operating, in particular,controlling a water or a wastewater treatment system, in accordance withone or more embodiments of the invention;

FIG. 3 is a flow diagram representatively illustrating at least aportion of acts utilized in controlling a water or a wastewatertreatment system, in accordance with one or more embodiments of theinvention;

FIG. 4 is a flow diagram representatively illustrating at least aportion of acts utilized in controlling a water or a wastewatertreatment system, in accordance with further embodiments of theinvention;

FIG. 5 is a graph showing measured parameters of a wastewater treatmentsystem controlled in accordance with one or more embodiments of theinvention;

FIG. 6 is a copy of a computer screen capture of a wastewater treatmentsystem controller showing a change in control modes (from a primarycontrol mode based on measured ORP to an alternate control mode based onfixed MCO output) in accordance with one or more embodiments of theinvention;

FIG. 7 is a copy of the computer screen capture of FIG. 6 highlighting asecond change in control modes (from the alternate control mode to theprimary control mode) in accordance with one or more embodiments of theinvention;

FIG. 8 is a copy of a computer screen capture of a wastewater treatmentsystem controller showing a changes in control modes (from a primarycontrol mode based on ORP to an alternate control mode based on measuredresidual chlorine level and back to the primary control mode) inaccordance with one or more embodiments of the invention; and

FIG. 9 is a copy of a computer screen capture of a wastewater treatmentsystem controller showing a change in control modes (from a primarycontrol mode based on ORP to an alternate control mode based on a fixedMCO level and back to the primary control mode) in accordance with oneor more embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is not limited in its application to the details ofconstruction and arrangement of components, systems or subsystems setforth in the description, including the various examples or asillustrated in the drawings. The invention is capable of otherembodiments and of being practiced or of being carried out in variousways. The terms used herein for the purpose of description should not beregarded as limiting. The use of the terms “comprising,” “including,”“carrying,” “having,” “containing,” “involving,” and the like are to beunderstood to be open-ended, i.e., to mean including but not limited to.Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth, with respect to the claims.

In accordance with one or more embodiments, the systems and techniquesof the invention can be characterized as optimizing control of watertreatment systems. The systems and techniques of the invention canidentify or at least facilitate identification of one or moreexceptional or other than normal conditions which can allow control ofthe treatment system in an alternate or secondary control type or mode.The systems and techniques of the invention can also be characterized asproviding a control system or controller or utilizing a control systemthat incorporates unique logic techniques to override primary controlwhen it may result in and reduce the likelihood of any unacceptableemission or discharge.

The systems and techniques of the invention can be further characterizedas accurately and reliably controlling chlorination and, in some cases,dechlorination systems. The systems and techniques of the invention canprovide a controller that can automatically switch from a primary, e.g.oxidation reduction potential, to a secondary, e.g. residual ppm,control based on predetermined, pre-selected, and/or programmedparameters.

The invention can be characterized as providing one or more controllersor techniques that can regulate the operation of one or more water oraqueous systems including, but not limited to, water and/or wastewatertreatment systems that typically involves adding, to the fluid to betreated, one or more oxidizing compounds or species and, in some cases,adding one or more neutralizing compounds or species. For example, thesystems and techniques of the invention can control or at least effectcontrol of addition one or more of the oxidizing compounds, and/orcontrol addition of one or more neutralizing compounds. In accordancewith one or more embodiments of the invention, operation of a water orwastewater treatment system 10 comprising a contact chamber, exemplarilyshown in FIG. 1, can be controlled utilizing one or more controllers 12based on one or more transmitted input signals, represented as dashedlines 14, 16, and 18, from one or more input device assemblies 20, 22,and 24 including one or more sensors 26, 28, and 30 disposed, typicallyin fluid communication with fluid to be treated such as water or anaqueous medium in the contact chamber, thereby providing a measure ofone or more operating parameters of the treatment system 10. Controller12 can transmit one or more output signals 32 and 33 to one or moreoutput devices 34 and 35 which can effect a change to the watertreatment system 10 by, for example, introducing a change in a flow rateof one or more added compounds or species, a change in a flow rate ofwater or wastewater to be treated, and, in some cases, a change inconcentration of one or more added compounds or species. Thus, thesystems and techniques of the invention can effect a change in one ormore controlled parameters in response to, or, in some cases, inanticipation of, a change in one or more operating parameters of thewater or wastewater treatment system.

Other aqueous systems that can suitably utilize the systems andtechniques of the invention include, for example, potable waterdisinfection systems, systems that utilize breakpoint chlorinationtechniques such as swimming pool or spa disinfection or treatmentsystems, industrial water systems, as well as chloraminization anddechloraminization systems.

In accordance with one or more embodiments of the invention, thecontroller can execute one or more steps or acts as exemplarily shown inthe flow diagram presented in FIG. 2. In some cases, one or moreembodiments of the invention pertinent to computer readable and/orwritable media can cause one or more controllers to execute one or moresteps or acts in the flow diagram exemplarily presented in FIG. 2.

For example, in accordance with one or more embodiments of theinvention, operation of controller 12 can be transferred from a manualstate to an automatic control state 112.

In the manual state, a predetermined amount of a compound can beintroduced from, for example, an output device 34 and/or 35 into thefluid to be treated in treatment system 10. Transfer from manual toautomatic can be initiated by an operator of the treatment facility or,in some cases, automatically upon attainment of one or morepredetermined conditions such as, but not limited to, a predeterminedconcentration, pH, temperature, and/or flow rate measurement or evenaccording to a schedule. Transfer can be performed when a steady-stateor near steady-state condition is identified. For example, automaticcontrol state can be assumed when a flow rate of an oxidizing agentrelative to a flow rate of the fluid to be treated is considered to beunchanged. In other cases, transfer to the automatic control state canbe performed when a target compound dosage is achieved. In still othercases, a target compound dosage can be calculated or determined upontransfer to the automatic control state. For example, upon achieving asteady state operating condition, transfer to the automatic state can beperformed; upon which, a dosage or rate of addition of the compoundrelative to the flow rate of fluid to be treated can be calculated andutilized as a target requirement during automatic operation.

In the automatic control state, the controller can, intermittently orcontinuously, check for one or more mode triggers 114. The mode triggercan be one or more conditions that typically would allow control of thetreatment system under one or more control modes. In the absence of amode trigger 114/No, the controller would typically supervise one ormore control parameters of the treatment system in a normal or primarycontrol mode 116. In the presence or identification of the mode trigger114/Yes, the controller would typically supervise one or more controlparameters in a secondary or an alternate control mode 118. Preferably,the controller, in primary control mode, can generate and transmit oneor more first or primary output signals, represented as references 32and 33 in FIG. 1, to one or more output devices 34 and 35, whichlikewise corresponds to one or more control parameters. The controller,in secondary or alternate control mode, can likewise generate andtransmit one or more secondary or alternate output signals, alsorepresented as references 32 and 33 in FIG. 1, to one or more outputdevices 34 and 35, which corresponds to one or more control parameters.The invention is not limited to the use of a single output device 34 or35 and can include multiple output devices in a variety ofconfigurations. For example, the controller can generate a first outputsignal in, for example, a first or primary control mode, to a firstoutput device to regulate addition, removal, and/or a change in a firstcontrol parameter; the controller can further generate a second outputsignal in, for example, a second or alternate control mode, to a secondoutput device to regulate addition, removal, and/or change in a secondcontrol parameter.

The one or more compounds can comprise one or more oxidizing agents thatcan neutralize or at least render inactive or inert at least oneundesirable species in the fluid to be treated. In accordance withfurther embodiments of the invention, the compound can comprise one ormore species that can affect the performance of the treatments system.For example, the compound can include a pH affecting or altering agentsuch as, but not limited to acids, bases, and buffers. Further, outputdevice 34 can comprise a source of an oxidizing agent that can oxidizeone or more undesirable species and treat the fluid in treatment system10. For example, one or more of output devices 34 and/or 35 can compriseany one of a halogen donor, a free radical species donor, as well ascombinations thereof. Output device 35 can comprise a source of a secondoxidizing agent and/or one or more neutralizing agents that can reactwith or otherwise remove or reduce the concentration of one or moretarget species such as an oxidizing agent from output device 34. Inother cases, output device 35 can comprise a source of a reducing agentthat reduce or maintain a concentration of a target species to atolerable or desired level. For example, output device 35 can comprise areducing agent that neutralizes the oxidizing agent dispensed fromoutput device 34 so that the concentration thereof in the dischargingwastewater stream satisfies regulated requirements.

Control in the alternate control mode can be transferred back to primarycontrol mode upon identification or realization of the absence of themode trigger or upon satisfaction of one or more other triggers orconditions.

In accordance with further embodiments, the system and techniques of theinvention can be characterized as performing in a primary control modeand, when appropriate, performing in an alternate control mode. In somecases, primary control can represent a normal control mode during whichthe systems and techniques of the invention are intended to operate andthe secondary or alternate control mode can represent a second controlor mode of operation of the systems and techniques of the invention. Theinvention can be further characterized as providing systems andtechniques that facilitate operational control of one or more watersystems by flexibly controlling one or more such systems in a firstcontrol mode as well as in other control modes. Thus, for example, thecontrollers of the invention can control or facilitate regulation,monitoring, and performance of one or more operating parameters of oneor more water systems between, or to and from, a first mode, a second oralternate mode, and, in some cases, a third or even a fourth controlmode.

Secondary control can be represented as providing a substitute controltechnique when the primary control indicates or is identified to beunder a predetermined, exceptional condition, or under an alarm orfailure condition. The systems and techniques of the invention canutilize one or more alternate channels that can provide a furtherindication of one or more operating parameters of the water system,preferably, independent of the primary, and/or the secondary controlmode.

Thus, for example, the invention can provide a method of controllingaddition of an oxidizing compound to a water treatment system. Themethod can comprise measuring a value of a process parameter of thewater treatment system, generating a first control signal in a firstcontrol mode when the value of the process parameter is within a firstrange, and generating a second control signal in a second control modewhen the value of the process parameter is within a second range.

In accordance with one or more embodiments, the systems and techniquesof the invention can identify, and, if appropriate, trigger an alternatecontrol mode, when, for example, an alarm condition is recognized. Forexample, primary control can utilize oxidation reduction potential tocontrol or regulate addition of one or more oxidizing compounds to waterin the water treatment system and secondary control utilizing residualconcentration of a specific or target species can be assumed when a highor low alarm condition is satisfied or exceeded. In other cases, primarycontrol can utilize residual concentration and secondary controlutilizing oxidation reduction potential can be assumed with a low or ahigh residual concentration alarm condition. In still other cases,primary control can be based on residual concentration and secondarycontrol utilizing oxidation reduction potential can be triggered uponidentification of a high or low oxidation reduction potential alarmcondition. In yet other cases, primary control can be based on residualconcentration and secondary control still utilizing residualconcentration, but with respect to a higher or lower set point referenceor target can be performed upon identification of a high or lowoxidation reduction potential alarm. In still further cases, primarycontrol can be based on a measured oxidation reduction potential andsecondary control based on measured residual concentration can bemaintained under a high or low residual oxidizer concentration alarmcondition. In yet further cases, primary control which can be based on ameasured oxidation reduction potential with secondary control basedresidual oxidizer concentration can be utilized until an alternatecontrol mode is assumed when a high or low residual concentration alarmcondition is present.

In accordance with one or more embodiments of the invention, primarycontrol based on, for example, a measured oxidation reduction potentialwith secondary control based on, for example, a measured residualconcentration, of a specific or target species, can be maintained untila high or low measured oxidation reduction potential alarm condition ispresent, during which alternate control based on one or more alternatesignals or channels can be utilized. In some cases, primary controlbased on a measured oxidation reduction potential along with secondarycontrol based on a measured residual concentration can be maintainedunless control can be effected utilizing one or more alternate channels,during conditions of a high or low residual concentrations. In stillother cases, primary control, based on residual concentration, alongwith secondary control, based on a measured oxidation reductionpotential, can be performed unless an alternate control channel isutilized during high or low residual concentration conditions. In yetother cases, primary control, based on residual concentration of one ormore species, along with secondary control, based on oxidation reductionpotential, can be performed unless control utilizing an alternatechannel is performed when high or low oxidation reduction potentialalarm conditions are present.

In accordance with one or more embodiments, the present invention canutilize primary control, based on residual concentration of one or morespecies, along with secondary control, based on oxidation reductionpotential, until or unless an unacceptable condition is presentcharacterized by an exceptional ratio of the value of the residualconcentration to the value of the oxidation reduction potential. In somecases, the present invention can utilize primary control, based onoxidation reduction potential, along with secondary control, basedresidual concentration of one or more species, until, or unless anunacceptable condition is present characterized by, for example, anexceptional ratio of the value of the residual concentration to thevalue of the oxidation reduction potential. Other exceptional ratioconditions may also be utilized such as, but not limited to, a ratio ofa concentration of one or more target species or even a ratio ofoxidizer concentration to target species to target speciesconcentration.

In accordance with one or more embodiments, the present invention cantrigger a change in control mode to effect control based on a secondaryinput channel when the primary input channel is identified to be faulty.The primary input channel can send or receive one or more signals 14,16, and 18 and a fault can be identified, for example, as any relevantcondition associated with an inoperable or malfunctioning sensor. Insome cases, the systems and techniques of the invention can assumecontrol based on a target dosage, or even a fixed, predetermined ordefault addition rate, upon switching to a secondary or tertiary controlcondition or mode. In still other cases, the invention can determine,and if appropriate, utilize, a third control parameter that can be basedon two or more primary input signals. For example, the third controlparameter can be represented as hypochlorous acid concentrationcalculated or estimated based on a measured pH and a measured freechlorine concentration.

The process parameter can correspond to an oxidation reduction potentialof water in the water treatment system. In accordance with someembodiments of the invention, the first control signal can be based on adifference between the value of the process parameter and a set point.In some cases, the first control signal can be further based on a rateof change of the value of the process parameter. In accordance withother embodiments of the invention, the second control signal can bebased on a difference between the value of the process parameter and analarm limit. The second control signal can be further based on a rate ofchange of the value of the process parameter.

In accordance with further embodiments, the systems and techniques ofthe invention can further comprise measuring a second process parameterof the water treatment system. In still further embodiments, the systemsand techniques of the invention can further comprise generating a thirdcontrol signal when a magnitude of a difference of a value of the secondprocess parameter and a second set point is less than a tolerance. Andin accordance with even further embodiments, the systems and techniquesof the invention can further comprise generating a fourth control signalin a fourth control mode when the magnitude of the difference of thevalue of the second process parameter and the second set point isgreater than the tolerance.

In accordance with one or more embodiments, the invention can provide amethod of controlling addition of an oxidizing compound to a watertreatment system. The method can comprise specifying a first set pointrepresenting a first desired operating condition of the water treatmentsystem, specifying a second set point and a tolerance representing asecond desired operating condition of the water treatment system,generating a first input signal corresponding to a first operatingparameter of the water treatment system, generating a second inputsignal corresponding to a second operating parameter of the watertreatment system, and generating a first output signal based on adifference between the first input signal and the first set point when adifference between the second input signal and the second set point isless than the tolerance. The method can further comprise generating asecond output signal based on the first input signal and a second setpoint when the difference between the second input signal and the secondset point is greater than the tolerance.

The first operating parameter can comprise an oxidation reductionpotential of the water in the water treatment system. The secondoperating parameter can comprise a concentration of the oxidizingspecies in the water treatment system. In accordance with someembodiments of the invention, generating the first output signal can bebased on a lag time of water flowing in the water treatment system and,in accordance with still other embodiments, generating the first outputsignal can be further based on a rate of change of one of the firstinput signal. Generating any of the output or control signals canutilize or involve at least one of adaptive, flow adjusted lag time,proportional, proportional-integral, proportional-derivative, andproportional-integral-derivative control algorithms.

In accordance with one or more embodiments, the invention can provide amethod of controlling addition of a compound to a water treatmentsystem. The method can comprise specifying a primary set pointrepresenting an operating condition of the water treatment system;measuring a primary operating parameter and a secondary operatingparameter of the water treatment system; generating a first outputsignal based on the primary operating parameter and the primary setpoint; identifying an alternate control mode when at least one conditionselected from the group consisting of a low first operating parameter, ahigh first operating parameter, a low second operating parameter, and ahigh second operating parameter is present; and generating an alternateoutput signal based on at least one of the primary operating parameterand the secondary operating parameter when the alternate control mode isidentified. The first operating parameter can correspond to an oxidationreduction potential of water in the water treatment system and thesecond operating parameter corresponds to a concentration of anoxidizing species in the water treatment system. The alternate outputsignal can be based on the primary operating parameter and an alternateset point.

The alternate output signal can be based on the secondary operatingparameter and an alternate set point. The first operating parameter cancorrespond to a concentration of an oxidizing species in the watertreatment system and the second operating parameter corresponds to anoxidation reduction potential of water in the water treatment system.

In accordance with one or more embodiments, the invention can provide awater treatment system. The water treatment system can comprise an inputdevice disposed to measure an operating parameter of the water treatmentsystem and generate a corresponding input signal; a controller disposedto receive and analyze the input signal and generate a first outputsignal based on a first difference between the input signal and a firstset point value and a second output signal based on a second differencebetween the input signal and a second set point value; and an outputdevice disposed to receive the first and second output signals andregulate addition of an agent to the water treatment system.

In accordance with one or more embodiments, the invention can provide awater treatment system comprising a first measurement device disposed tomeasure a first parameter of the water treatment system and generate afirst input signal, a second measurement device disposed to measure asecond parameter of the water treatment system and generate a secondinput signal, a controller disposed to receive and analyze the firstinput signal and the second input signal and generate a first outputsignal when a difference between the second input signal and a secondset point value is less than a tolerance and generate a second outputsignal when the difference between the second input signal and the setpoint value is greater than the tolerance, and an output device disposedto receive at least one of the first and second output signals andregulate addition of an oxidizer to the water treatment system. Thefirst parameter can correspond to an oxidation reduction potential ofwater in the water treatment system and, in some cases, the secondparameter can correspond to a concentration of the oxidizer in the watertreatment system. The first set point value can be ORP at, for example,about 400 mV or any predetermined value or range.

In accordance with one or more embodiments, the invention can provide awater treatment system comprising a first sensor or measurement devicedisposed in the water treatment system such as a sensor that can providean indication of an oxidation reduction potential (ORP, also referred toas HRR) of water or wastewater in the treatment system; a second sensordisposed in the water treatment system such as an amperometric sensor orany similar sensor that can provide an indication or representation ofconcentration of one or more species or agents in the water orwastewater; a means for controlling addition of an oxidizing species oragent to the water or wastewater in the treatment system in response toa signal from, for example, at least one of the ORP sensor and theamperometric sensor; and a means for identifying and controllingaddition of the oxidizing species in an alternate control mode inresponse to a signal from, for example, at least one of the sensors,such as the ORP sensor or the amperometric sensor, when at least onecondition selected from the group consisting of a low first operatingparameter, a high first operating parameter, a low second operatingparameter, and a high second operating parameter is present.

The present invention is not limited to any particular type of sensingdevice and can utilize one or more sensing devices and/or one or moretypes of sensor design such as, but not limited to, electrochemicaldevices, membrane-based devices, as well as ultrasonic-based sensor forsensing chlorine, combined chlorine, bromine, hypochlorus acid, chlorinedioxide species concentration, and/or pH. Thus, sensor or measurementdevices such as amperometric, oxidation reduction potential,tri-amperometric and membrane devices can be utilized in the systems andtechniques of the present invention.

The output signal of the controllers of the present invention cancontrol, actuate, and/or energize devices such as pumps, valves, andmotors. The controller output signal may be generated to influence thefeed rate of oxidizers such as chlorine, hypochlorite, bromine and otherprocess chemicals. In addition the controller output signal may beconfigured to influence the feed rate of reducing agents such as sulfurdioxide, sodium bisulfite and other process chemicals.

The controllers of the invention can include one or more processor andcan, for example, comprise a computer. One or more embodiments of theinvention may include, among other components, a plurality of knowncomponents such as one or more processors, memory systems, disk storagesystems, network interfaces, and busses or other internal communicationlinks interconnecting the various components. One or more of thecomponents of the systems of the invention may reside on a singlecontrol system e.g., a single microprocessor, or one or more componentsmay reside on separate, discrete systems, e.g. a network of computers.Further, one or more components of the systems of the invention may bedistributed or represented across multiple control systems. Differentaspects or portions of the components of system 10 may reside or berepresented in different areas of memory (e.g., RAM, ROM, disk, etc.) onthe control system. In some cases, different portions of the controlsystem may be present or utilized in one or more locations remotelypositioned from each other and/or water system 10. Thus, for each of theone or more systems that can include one or more components of thesystems of the invention, each of the systems and/or components thereofmay reside or be utilized in one or more locations.

The methods of the invention, acts thereof, and various embodiments andvariations of the methods and acts, individually or in combination, maybe defined by computer-readable signals tangibly embodied on acomputer-readable medium, for example, a non-volatile recording medium,an integrated circuit memory element, or a combination thereof. Suchsignals may define instructions, for example, as part of one or moreprograms that, as a result of being executed by a computer, instruct thecomputer to perform one or more of the methods or acts described herein,and/or various embodiments, variations and combinations thereof. Suchinstructions may be written in any of a plurality of programminglanguages, for example, Java, Visual Basic, C, C#, or C++, Fortran,Pascal, Eiffel, Basic, COBAL, etc., or any of a variety of combinationsthereof. The computer-readable medium on which such instructions arestored may reside on one or more of the components of system describedabove, and may be distributed across one or more of such components.

The computer-readable medium may be transportable such that theinstructions stored thereon can be loaded onto any computer systemresource to implement the aspects of the present invention discussedherein. In addition, it should be appreciated that the instructionsstored on the computer-readable medium, described above, are not limitedto instructions embodied as part of an application program running on ahost computer. Rather, the instructions may be embodied as any type ofcomputer code (e.g., software or microcode) that can be employed toprogram a processor to implement the above-discussed aspects of thepresent invention.

In accordance with one or more embodiments, the invention can provide acomputer-readable medium having computer-readable signals stored thereonthat define instructions that, as a result of being executed by acomputer, instruct the computer to perform a method of controllingaddition of an oxidizer compound to a water treatment system comprisingacts of generating a first control signal in a first control mode when avalue of a process parameter of the water treatment system is within afirst range and generating a second control signal in a second controlmode when the value of the process parameter is within a second range.

The first control signal can be based on a difference between the valueof the process parameter and a set point. The first control signal canbe further based on a rate of change of the value of the processparameter. The process parameter can correspond to an oxidationreduction potential of water in the water treatment system.

In accordance with one or more embodiments, the invention can provide acomputer-readable medium having computer-readable signals stored thereonthat define instructions that, as a result of being executed by acomputer, instruct the computer to perform a method of controllingaddition of an oxidizer compound to a water treatment system comprisingacts of receiving a first input signal from a first input devicedisposed to measure a first operating parameter of the water treatmentsystem, receiving a second input signal from a second input devicedisposed to measure a second operating parameter of the water treatmentsystem, generating a first output signal based on the first input signaland a first set point when a difference between the second input signaland the second set point value is less than a tolerance, and generatinga second output signal based on the first input signal and a second setpoint when the difference between the second input signal and the secondset point value is greater than the tolerance.

Although several of the steps or acts described herein have beendescribed in relation to being implemented on a computer system orstored on a computer-readable medium, aspects of the invention are notlimited as such, as steps or acts may be implemented without use of acomputer by, for example, a person.

Various embodiments according to the invention may be implemented on oneor more computer systems. These computer systems may be, for example,general-purpose computers such as those based on any one or morePENTIUM® processors available from Intel Corporation, Santa Clara,Calif.; PowerPC™ processors available from Motorola, Inc., Schaumburg,Ill.; UltraSPARC® processors available from Sun Microsystems, Inc.,Santa Clara, Calif.; PA-RISC architecture based processors availablefrom, for example, Hewlett-Packard Corporation, Palo Alto, Calif.; orany other type of processor. It should be appreciated that one or moreof any type computer system may be used to control one or morewastewater treatment systems in one or more control modes according tothe embodiments of the invention. Further, the software design systemmay be located on a single computer or may be distributed among aplurality of computers attached by, for example, a communicationssystem, or network.

Further, a general-purpose computer system according to one embodimentof the invention can be configured to perform to control one or morewastewater treatment systems in one or more control modes. It should beappreciated that the system may perform other functions, including, forexample, monitor pH, monitor material inventories, create, and/or sendreports, including, for example, status reports or even alarm reports,to one or more stations, individuals, or organizations. The invention isnot limited to having any particular function or set of functionsdescribed above.

For example, various aspects of the invention may be implemented asspecialized software, embodied, for example, in a computer-readablemedium, executing in a general-purpose computer system. The computersystem may include a processor connected to one or more memory devices,such as a disk drive, flash drive, memory, or other device for storingdata, which can be used for storing programs and data during operation.Components of the computer system may be coupled by one or moreinterconnection mechanisms, which may include one or more busses, e.g.,between components that are integrated within a same machine, and/or anetwork, e.g., between components that reside on separate discretemachines. The interconnection mechanism preferably enablescommunications, e.g., data, instructions, to be exchanged between systemcomponents of the computer system or even the controller, which canutilize wired or by wireless communication techniques. The computersystem can also include one or more input devices such as, but notlimited to keyboards, mouse, trackballs, microphones, touch screens, aswell as one or more output devices such as, but not limited to, printingdevices, display screens, alarm indicators, and speakers. In addition,the computer system may contain one or more interfaces that connect thecomputer system to a communication network, in addition or as analternative to the network that may be formed by one or more of thecomponents of system.

The systems of the invention can include one or more computer readableand writeable nonvolatile recording media in which signals can be storedthat define a program or algorithm to be executed by the processor orinformation stored on or in the medium to be processed by the program.The medium may have various forms and can be utilized as, for example, adisk, or flash memory. Typically, in operation, the processor causesdata to be read from the nonvolatile recording medium into anothermemory structure that can allow for faster access to the information bythe processor than does the medium. This memory can be a volatile,random access memory such as a dynamic random access memory (DRAM) orstatic memory (SRAM). It may be located in a storage system or in amemory system in communication with one or more processors. In somecases, the processor can manipulate the data within one or moreintegrated circuit memory structures and can then copy the data to themedium after processing is completed. A variety of mechanisms can beutilized to manage data movement between the medium and the integratedcircuit memory element, and the invention is not limited thereto.Further, various types of memory structures or subsystems can beutilized and the invention is not limited to a particular memory systemor storage system.

The controllers of the invention may utilize and/or includespecially-programmed, special-purpose hardware including, for example,application-specific integrated circuit (ASIC) devices. Various aspectsof the invention may be implemented in software, hardware or firmware,or any combination thereof. Further, such methods, acts, systems, systemelements and components thereof may be implemented as part of thecontroller described herein or as an independent component thereof.

The various systems of the invention may comprise one or moregeneral-purpose computer system that is programmable using any suitablehigh-level computer programming language. The controllers of theinvention may be also implemented using specially programmed, specialpurpose hardware. The controllers of the invention can utilize one ormore processors or microprocessors which are typically commerciallyavailable processors and can be, for example, PENTIUM® processorsavailable from Intel Corporation, Santa Clara, Calif. Other commerciallyavailable processors can be utilized including any that can employ oneor more operating systems which may be, for example, WINDOWS® 95,WINDOWS® 98, WINDOWS® NT, WINDOWS® 2000 (WINDOWS® ME) or WINDOWS® XP®operating systems, each available from Microsoft Corporation, MAC® OSSystem X® available from Apple Computer, Solaris operating systemavailable from Sun Microsystems, or UNIX operating system available fromvarious sources such as Linux. Other operating systems may be used, andthe present invention is not limited to any particular implementation.

Typically, the processor and operating system together define a computerplatform for which application programs in high-level programminglanguages are written. It should be understood that the invention is notlimited to a particular computer system platform, processor, operatingsystem, or network. Also, the present invention is not limited to aspecific programming language or computer system. Further, it should beappreciated that other appropriate programming languages and otherappropriate computer systems could also be used.

One or more portions of the systems of the invention may be distributedacross one or more computers (not shown) coupled to a communicationsnetwork. These computer systems may also be general-purpose computersystems. For example, various aspects of the invention may bedistributed among one or more computer systems configured to provide aservice (e.g., servers) to one or more client computers, or to performan overall task as part of a distributed system. For example, variousaspects of the invention may be performed on a client-server system thatincludes components distributed among one or more server systems thatperform various functions according to various embodiments of theinvention. These components may be executable, intermediate, e.g., IL,or interpreted, e.g., Java, code which communicate over a communicationnetwork, e.g., the Internet, using a communication protocol, e.g.,TCP/IP. Thus, one or more components may be located remotely from thetreatment system and be in communication therewith through any one ormore techniques including, for example, by radio, network, virtualnetwork, or even through the Internet.

It should be appreciated that the invention is not limited to executingon any particular system or group of systems. Also, the invention is notlimited to any particular distributed architecture, network, orcommunication protocol.

Various embodiments of the present invention may be programmed using anobject-oriented programming language, such as SmallTalk, Java, C++, Ada,or C# (C-Sharp). Other object-oriented programming languages may also beused. Alternatively, functional, scripting, and/or logical programminglanguages may be used. Various aspects of the invention may beimplemented in a non-programmed environment (e.g., documents created inHTML, XML or other format that, when viewed in a window of a browserprogram, render aspects of a graphical-user interface (GUI), or performother functions). Various aspects of the invention may be implemented asprogrammed or non-programmed elements, or combinations thereof.

The above-described embodiments of the present invention can beimplemented in any of numerous ways. For example, the above-discussedfunctionality for identifying a control mode change can be implementedusing hardware, software or a combination thereof. When implemented insoftware, the software code can be executed on any suitable processor.It should further be appreciated that any single component or collectionof multiple components of the computer system that perform the functionsdescribed above can be generically considered as one or more controllersthat control the above-discussed functions. The one or more controllerscan be implemented in numerous ways, such as with dedicated hardware, orusing a processor that is programmed using microcode or software toperform the functions recited above.

In this respect, one implementation of the embodiments of the presentinvention comprises at least one computer-readable medium (e.g., acomputer memory, a floppy disk, a compact disk, a tape, flash memory,etc.) encoded with a computer program (i.e., a plurality ofinstructions), which, when executed on a processor, performs theabove-discussed functions of the embodiments of the present invention.The computer-readable medium can be transportable such that the programstored thereon can be loaded onto any computer system resource toimplement the aspects of the present invention discussed herein. Inaddition, it should be appreciated that the reference to a computerprogram which, when executed, performs the above-discussed functions, isnot limited to an application program running on the host computer.Rather, the term computer program is used herein in a generic sense toreference any type of computer code, e.g., software or microcode, whichcan be employed to program a processor to implement the above-discussedaspects of the present invention.

EXAMPLES

The function and advantages of these and other embodiments of theinvention can be further understood from the examples below, whichillustrate the benefits and/or advantages of the one or more systems andtechniques of the invention but do not exemplify the full scope of theinvention.

Example 1

FIG. 3 schematically shows a flow diagram of a control technique thatcan be implemented to control chlorination and/or dechlorination of atreatment system, exemplarily shown in FIG. 1, in accordance with one ormore embodiments of the invention.

The controller can be operated by transferring 212 from manual controlstate to an automatic control state when suitable or desired by anoperator of the treatment system. Upon transfer 212, the controllertypically determines 213 a current dosage, which can be used as a targetrequirement pertinent to operation of the treatment system. For example,the dosage can be determined by relating a rate of addition of acompound, such chlorine, to a rate of fluid flow. The ORP of the fluidto be treated in the treatment system can also be measured by utilizingone or more sensors. Thus, the controller can utilize the determineddosage and seek to achieve this dosage as one operating requirement.

The controller can check or determine if a change in control modes isappropriate by, for example, testing 214 for an ORP high alarmcondition. If a control mode change is not detected 214/No, control ofthe treatment system is performed under a normal or primary control mode216. If a control mode change is detected 214/Yes, control of thetreatment system is performed under an alternate control mode 218.

Under primary control mode, a control channel can regulate addition ofone or more compounds to the treatment system. For example, thecontroller can regulate addition of an oxidizing agent, such as chlorineor other sanitizers, to achieve an ORP set point of about 475 mV inwater in the treatment system.

Under secondary control, the controller can regulate addition of thesame or different compounds, with or without a change in an operatingparameter. For example, the controller can regulate addition of chlorinebased on an alternate ORP set point equal to the high ORP alarm value,e.g. about 700 mV, or to a low ORP alarm value. The controller canthereby generate an alternate output signal based on, for example, adifference between a measured process parameter and the alternate targetset point, e.g. the difference between the measured ORP and thealternate ORP set point of 700 mV.

Control under the primary or alternate control mode can further comprisemodifying the output signal by utilizing flow pace techniques 217 thatincorporate or compensate for operating fluctuations of the fluid to betreated. For example, the controller can modify the output signal basedon the measured ORP value and a rate of change of the measured ORPvalue, e.g. the output signal can be weighted to be based on adifference between the ORP set point of 700 mV and a rate of change ofthe measured ORP.

The controller can utilize flow adjusted lag time (FALT or T_(f))control techniques. T_(f) can be calculated 215 to compensate forvariations in measured flow rate such that T_(f)=(T₁·K_(f)·F_(%)) whereT₁ is the system's inherent lag time, K_(f) is a flow factor, and F_(%)is an averaged flow rate, in percent relative to a design flow rate ofthe system. FALT is the calculated time based on the change in incomingflow relative to the fixed sensor(s) location(s).

The controller can query whether the flow adjusted lag time has elapsed;if so 219/Yes, then the controller can proceed to calculate a change inmodified or modulated control output (MCO) based on the ORP set pointand the slope of the measured ORP; otherwise 219/No, the controller canreturn to querying 214 to determine if a control mode change isappropriate.

MCO is the control algorithm that varies the output of the controllerbased on the measured sensor inputs and the ORP set point. FALT isutilized to determine the time required between MCO changes.

Example 2

FIG. 4 schematically shows a flow diagram of another control techniquethat can be implemented to control chlorination and/or dechlorination ofa treatment system, exemplarily shown in FIG. 1, in accordance withfurther embodiments of the invention. The control system in thisexample, like the control system described in Example 1, can alsoperform one or more query operations 314 to identify whether controlshould be performed in a primary control mode 316 or to control in asecondary or alternate control mode 318. As with the previous example,the change in control mode can be triggered by, for example, recognizinga high ORP level. However, the alternate control mode 318, as in thisexample, can be based on a second measured parameter, exemplarily shownas the amperometric measurement with a predetermined or pre-selected setpoint value of about 7.1 ppm.

Example 3

A wastewater treatment system (SWWTP), schematically shown in FIG. 1 wasoperated utilizing a STRANTROL 960 controller, available from USFilter,Stranco Products, Bradley, Ill. An oxidizing agent, chlorine, fromoutput device 34 was fed to disinfect the wastewater. A reducing agent,a sulfite species, from output device 35 was introduced to the treatedwastewater before discharge from the contact chamber to reduce theconcentration of chlorine to within regulated levels. Flow of water tobe treated is shown from upper left to lower right.

With reference to FIGS. 1-3, in primary control mode 116 and 216, upontransfer 112 and 212 from manual to automatic control, controller 12calculated 213 a dosage based on the flow of wastewater (flow meterinput) and current output to oxidant feeder (chlorinator). Controller 12also calculated 215 a flow adjusted lag time according to the formulaT _(f)=(T ₁ ·K _(f) ·F _(%))

where T₁ is the system's inherent lag time, K_(f) is a flow factor, andF_(%) is an averaged flow rate, in percent relative to a design flowrate of the treatment system.

Controller 12 further modified 217 the output signal by incorporatingflow pacing techniques. The flow paced output signal was generated basedon a measured flow rate of the wastewater to be treated by a flow meter(not shown).

If FALT has not expired 219/No, controller 12 performed primary control216 by generating an output signal to output device 34 based on the flowrate of the wastewater stream.

If FALT has expired, a new MCO was calculated 220 based on the ORPdeviation from set point and the rate of change (slope) of the measuredORP of the wastewater stream, specifically, the rate of change of ORPwithin the previous 10% of the FALT period. The control sequence wasthen returned to calculating the dosage based on the new MCO 213.

FIG. 5 is a copy of a computer display showing the dosage value 510 (inppm) of the chlorine oxidizer as a function of elapsed time. As shown,at a time of about 14:35, the dosage was relatively steady and thecorresponding controller-generated output 512 varied based on the flowrate 514 of the wastewater. At about 14:52, the FALT has expired 219/Yesand a new MCO was calculated 212 based on the deviation from the ORP 516set point (shown as HRR) and its slope. A new dosage was then calculated213 based on the new MCO and the measured flow rate 514. A new FALT wasalso determined 215. Control was based on the new, revised (lower)dosage. Flow pacing 217 proportionally biased the output signal to thechlorine feeder (output device) relative to the currently measured flowrate 514.

The measured ORP 516 (mV) (slightly above the ORP set point of about 475mV) of the wastewater is also shown as a function of time.

Control was performed in primary mode throughout the duration shown inFIG. 5 because the measured ORP was maintained within a desiredtolerance band even with fluctuating wastewater stream flow rate.

Example 4

In this example, the wastewater treatment system was operated alsoutilizing a STRANTROL 960 controller, available from USFilter, StrancoProducts, Bradley, Ill., under primary control as substantiallydescribed in Example 3 and was operated under secondary control that wastriggered by a high alarm condition.

FIG. 6 is a copy of a computer screen capture of the SWWTP processconditions showing measured operating conditions and control parametersas a function of time. Prior to a time of about 19:34 (indicated by thevertical bars 610 and captioned 7:34 p.m. in both upper and lower rightframes), control was performed under primary control, based on an ORPset point as substantially described in Example 3. At about 19:34, analarm condition (chlorine level greater than 2 ppm) was identifiedcorresponding to an amperometrically-measured high chlorine residuallevel (about 2.16 ppm) and displayed as “Ch1 2ndary Cl input” 612.Shortly thereafter, control mode was changed to an alternate controlmode identified as “START Ch1 Alarm override ctrl.” FIG. 6 also showsthe duration of the alarm condition 614 (labeled as “2ndary1 alm”) andthe alternate control mode 616 (labeled as “Ovrd Ctrl1”). In thealternate control mode, the controller was configured to produce a fixedoutput 618 (labeled as “Ch1 MCO (%)”) of about 50% (shown as 49.5% inFIG. 7) additionally above the point where it was feeding before thealarm condition (38.8%). FIG. 6 also shows the responses, increasedchlorine 620 (“Ch1 dosage”) associated the corresponding increase, andmeasured ORP 622 (“Ch1 Pri HRR input”).

FIG. 7 is a copy of a computer screen capture of the SWWTP processconditions wherein the bar 610 has been advanced about five minutes(captioned as “7:39 p.m.”) after its position shown in FIG. 6. At thispoint, the alternate control mode ended (labeled as “END Ch1 Alarmoverride ctrl”) and control was performed under primary control. Thiscontrol change was initiated because the alarm initiating the override“2ndary high alarm” fell below the alarm point (about 2.00 ppm) andprimary control resumed at the current control dosage (about 5.28 ppm upfrom about 4.01 ppm).

Also shown in FIGS. 6 and 7 is a recurrence of the change to alternatecontrol mode for about six seconds at about 19:39:34 to about 19:49:40.In this case, because the output was already at about the additional 50%level, no control response is shown.

At about 19:39:41 (“END Ch1 Alarm override ctrl”), the controllerswitched to primary control because the alarm condition ended.

At about 20:07, the 2ndary input (Cl ppm) dropped to the low alarm pointof about 0.50 ppm, which in turn, initiated an override to switchcontrol to the 2ndary input at a set point of about 1.25 ppm. Thiscaused the MCO to be recalculated based upon a deviation from set pointusing the current control input (0.50 ppm) and the setpoint of about1.25 ppm, which increased the output from about 50% to about 100%. Thecontroller flow-paced for a few minutes at a dosage of about 10.02 ppmuntil about 20:11:25 when the low chlorine alarm rose above thehysteresis value of about 0.05 ppm and then the alarm and overridecontrol reset. The primary ORP (also referred to as HRR) control resumedat about 20:11:26 at a dosage of about 9.98 ppm and a setpoint of about480 mV. Before the next FALT expiration at about 20:26, the 2ndary inputreached high alarm point (about 3 ppm) which caused a fixed outputoverride condition at about 50%. This override condition existed or wasmaintained until the 2ndary residual input dropped below the alarm pointat about 20:39:10 then bounced back into override and back out at about20:39:14. After this recovery the system resumed ORP primary control ata setpoint of about 480 mV and all alarms were reset.

Example 5

In this example, the wastewater treatment system as described in theprevious examples was controlled utilizing a primary control mode (basedon ORP) and a secondary control mode (based on measured chlorineresidual).

As shown in FIG. 8, which is a copy of a computer screen display of thewastewater treatment system controller, alternate control mode fromprimary control mode (based on ORP) was triggered at about 04:40:59(indicated by the vertical bars 810) when the input signal correspondingto amperometrically measured chlorine level 812 in the wastewater wasdetermined to be (about 0.50 ppm) below the lower alarm level. Thealternate control mode was based on total chlorine level residual. Inthis alternate control, the MCO 814 and the dosage 816 was ramped up toraise the residual chlorine level. After several minutes, a detectedrise in the residual chlorine level at about 04:54 triggered a change incontrol mode to revert to primary control, based on ORP.

Example 6

In this example, the wastewater treatment plant as described in theprevious examples was operated under a primary control mode (based onORP) and an alternate control mode (fixed output level). A high ORPlevel (599 mV) triggered (at about 06:51) the change from the primarycontrol mode to the alternate control mode. Control based on fixed MCOoutput level 912, with corresponding chlorine dosage rate 914, which wasflow paced based on the flow rate 916, was performed until the measuredORP 918 reduced to within acceptable limits.

Example 7

The following table lists overrides that can be utilized in the aboveexamples to trigger or initiate a control mode change. 1st PriorityOverride Ch1 1st priority ovrd src/type Pri high alarm fixed out ovrdCh1 Pri HRR high alarm fixed out 35.0% 2nd Priority Override Ch1 2ndpriority ovrd src/type Pri low alarm dosage ovrd Ch1 Pri HRR Low alarmdosage out 10.00 ppm (dsg) Ch1 Pri HRR low alarm fixed out 60.0% 3rdPriority Override Ch1 3rd priority ovrd src/type 2ndary low alarm 2ndaryctrl ovrd Ch1 3rd priority ovrd feed pt 1.25 ppm 4th Priority OverrideCh1 4th priority ovrd src/type 2ndary high alarm alt Pri feed point ovrdCh1 4th priority ovrd feed pt 400 mV

A 4^(th) priority override (such as 2ndary Cl Residual High alarm) thatcan cause the controller to change to a 400 mV set point, for example,can be ignored if a higher priority alarm (e.g. Primary HRR high alarm)occurs, and control can change to the higher priority control override(e.g. fixed output of 35%).

Having now described some illustrative embodiments of the invention, itshould be apparent to those skilled in the art that the foregoing ismerely illustrative and not limiting, having been presented by way ofexample only. Numerous modifications and other embodiments are withinthe scope of one of ordinary skill in the art and are contemplated asfalling within the scope of the invention. In particular, although manyof the examples presented herein involve specific combinations of methodacts or system elements, it should be understood that those acts andthose elements may be combined in other ways to accomplish the sameobjectives. Acts, elements and features discussed only in connectionwith one embodiment are not intended to be excluded from a similar rolein other embodiments. It is to be appreciated that various alterations,modifications, and improvements can readily occur to those skilled inthe art and that such alterations, modifications, and improvements areintended to be part of the disclosure and within the spirit and scope ofthe invention. For example, the invention contemplates the use ofvarious wired or wireless protocols to effect communication betweensystems, subsystems, and/or components thereof. For example, the varioussystems, subsystems and techniques of the invention can be implementedutilizing any suitable communication method including wired and wirelessprotocols. The invention contemplates retrofitting or modifying existingfacilities or systems to incorporate the features, systems, subsystems,and techniques of the invention. Moreover, it should also be appreciatedthat the invention is directed to each feature, system, subsystem, ortechnique described herein and any combination of two or more features,systems, subsystems, or techniques described herein and any combinationof two or more features, systems, subsystems, and/or methods, if suchfeatures, systems, subsystems, and techniques are not mutuallyinconsistent, is considered to be within the scope of the invention asembodied in the claims. Further, any of the means-plus-functionlimitations recited in the following claims, the means are not intendedto be limited to the means disclosed herein for performing the recitedfunction, but are intended to cover in scope any means, known now orlater developed, for performing the recited function. Use of ordinalterms such as “first,” “second,” “third,” and the like in the claims tomodify a claim element does not by itself connote any priority,precedence, or order of one claim element over another or the temporalorder in which acts of a method are performed, but are used merely aslabels to distinguish one claim element having a certain name fromanother element having a same name (but for use of the ordinal term) todistinguish the claim elements. Further, as used herein, “plurality”means two or more. As used herein, a “set” of items may include one ormore of such items.

Those skilled in the art should appreciate that the parameters andconfigurations described herein are exemplary and that actual parametersand/or configurations will depend on the specific application in whichthe systems and techniques of the invention are used. Those skilled inthe art should recognize or be able to ascertain, using no more thanroutine experimentation, equivalents to the specific embodiments of theinvention. It is therefore to be understood that the embodimentsdescribed herein are presented by way of example only and that, withinthe scope of the appended claims and equivalents thereto; the inventionmay be practiced otherwise than as specifically described.

1. A method of controlling addition of an oxidizing compound to a watertreatment system comprising: measuring a value of a process parameter ofthe water treatment system; generating a first control signal in a firstcontrol mode when the value of the process parameter is within a firstrange; and generating a second control signal in a second control modewhen the value of the process parameter is within a second range.
 2. Themethod of claim 1, wherein the process parameter corresponds to anoxidation reduction potential of water in the water treatment system. 3.The method of claim 1, wherein the first control signal is based on adifference between the value of the process parameter and a set point.4. The method of claim 3, wherein the first control signal is furtherbased on a rate of change of the value of the process parameter.
 5. Themethod of claim 1, wherein the second control signal is based on adifference between the value of the process parameter and an alarmlimit.
 6. The method of claim 5, wherein the second control signal isfurther based on a rate of change of the value of the process parameter.7. The method of claim 1, further comprising measuring a second processparameter of the water treatment system.
 8. The method of claim 7,further comprising generating a third control signal when a magnitude ofa difference of a value of the second process parameter and a second setpoint is less than a tolerance.
 9. The method of claim 8, furthercomprising generating a fourth control signal in a fourth control modewhen the magnitude of the difference of the value of the second processparameter and the second set point is greater than the tolerance. 10.The method of claim 2, further comprising actuating a valve to regulatethe addition of the oxidizing compound based on at least one of thefirst and second control signals.
 11. A method of controlling additionof an oxidizing compound to a water treatment system comprising:specifying a first set point representing a first desired operatingcondition of the water treatment system; specifying a second set pointand a tolerance representing a second desired operating condition of thewater treatment system; generating a first input signal corresponding toa first operating parameter of the water treatment system; generating asecond input signal corresponding to a second operating parameter of thewater treatment system; generating a first output signal based on adifference between the first input signal and the first set point when adifference between the second input signal and the second set point isless than the tolerance; and generating a second output signal based onthe first input signal and a second set point when the differencebetween the second input signal and the second set point is greater thanthe tolerance.
 12. The method of claim 11, wherein the first operatingparameter is an oxidation reduction potential.
 13. The method of claim12, wherein the second operating parameter is a concentration of theoxidizing species in the water treatment system.
 14. The method of claim13, wherein generating the first output signal is based on a lag time ofwater flowing in the water treatment system.
 15. The method of claim 14,wherein generating the first output signal is further based on a rate ofchange of the first input signal.
 16. The method of claim 14, whereingenerating at least one of the first and second output signals utilizesat least one of adaptive, proportional, proportional-integral,proportional-derivative, and proportional-integral-derivative controlalgorithms.
 17. A method of controlling addition of a compound to awater treatment system comprising: specifying a primary set pointrepresenting an operating condition of the water treatment system;measuring a primary operating parameter and a secondary operatingparameter of the water treatment system; generating a first outputsignal based on the primary operating parameter and the primary setpoint; identifying an alternate control mode when at least one conditionselected from the group consisting of a low first operating parameter, ahigh first operating parameter, a low second operating parameter, and ahigh second operating parameter is present; and generating an alternateoutput signal based on at least one of the primary operating parameterand the secondary operating parameter when the alternate control mode isidentified.
 18. The method of claim 17, wherein the first operatingparameter corresponds to an oxidation reduction potential of water inthe water treatment system and the second operating parametercorresponds to a concentration of an oxidizing species in the watertreatment system.
 19. The method of claim 18, wherein the alternateoutput signal is based on the primary operating parameter and analternate set point.
 20. The method of claim 18, wherein the alternateoutput signal is based on the secondary operating parameter and analternate set point.
 21. The method of claim 17, wherein the firstoperating parameter corresponds to a concentration of an oxidizingspecies in the water treatment system and the second operating parametercorresponds to an oxidation reduction potential of water in the watertreatment system.
 22. A water treatment system comprising: an inputdevice disposed to measure an operating parameter of the water treatmentsystem and generate a corresponding input signal; a controller disposedto receive and analyze the input signal and generate a first outputsignal, in a first control mode, based on a first difference between theinput signal and a first set point value and a second output signal, ina second control mode, based on a second difference between the inputsignal and a second set point value; and an output device disposed toreceive the first and second output signals and regulate addition of anagent to the water treatment system.
 23. A water treatment systemcomprising: a first measurement device disposed to measure a firstparameter of the water treatment system and generate a first inputsignal; a second measurement device disposed to measure a secondparameter of the water treatment system and generate a second inputsignal; a controller disposed to receive and analyze the first inputsignal and the second input signal and generate a first output signalwhen a difference between the second input signal and a second set pointvalue is less than a tolerance and generate a second output signal whenthe difference between the second input signal and the set point valueis greater than the tolerance; and an output device disposed to receiveat least one of the first and second output signals and regulateaddition of an oxidizer to the water treatment system.
 24. The watertreatment system of claim 23, wherein the first parameter corresponds toan oxidation reduction potential of water in the water treatment system.25. The water treatment system of claim 24, wherein the second parametercorresponds to a concentration of the oxidizer in the water treatmentsystem.
 26. The water treatment system of claim 25, wherein the firstset point value is about 400 mV.
 27. A water treatment systemcomprising: an ORP sensor disposed in the water treatment system; anamperometric sensor disposed in the water treatment system; a means forcontrolling addition of an oxidizing species to water in the watertreatment system in response to a signal from at least one of the ORPsensor and the amperometric sensor; and a means for identifying andcontrolling addition of the oxidizing species in an alternate controlmode in response to a signal from at least one of the ORP sensor and theamperometric sensor when at least one condition selected from the groupconsisting of a low first operating parameter, a high first operatingparameter, a low second operating parameter, and a high second operatingparameter is present.
 28. A computer-readable medium havingcomputer-readable signals stored thereon that define instructions that,as a result of being executed by a computer, instruct the computer toperform a method of controlling addition of an oxidizer compound to awater treatment system comprising acts of: generating a first controlsignal in a first control mode when a value of a process parameter ofthe water treatment system is within a first range; and generating asecond control signal in a second control mode when the value of theprocess parameter is within a second range.
 29. The computer-readablemedium of claim 28, wherein the act of generating the first controlsignal is based on a difference between the value of the processparameter and a set point.
 30. The computer-readable medium of claim 29,wherein the act of generating the first control signal is further basedon a rate of change of the value of the process parameter.
 31. Thecomputer-readable medium of claim 28, wherein the process parametercorresponds to an oxidation reduction potential of water in the watertreatment system.
 32. A computer-readable medium havingcomputer-readable signals stored thereon that define instructions that,as a result of being executed by a computer, instruct the computer toperform a method of controlling addition of an oxidizer compound to awater treatment system comprising acts of: receiving a first inputsignal from a first input device disposed to measure a first operatingparameter of the water treatment system; receiving a second input signalfrom a second input device disposed to measure a second operatingparameter of the water treatment system; generating a first outputsignal based on the first input signal and a first set point when adifference between the second input signal and the second set pointvalue is less than a tolerance; and generating a second output signalbased on the first input signal and a second set point when thedifference between the second input signal and the second set pointvalue is greater than the tolerance.